Push-button operator with locking means



Filed Oct. 23, 1959 C. C. DAVIS ETAL PUSH-BUTTON OPERATOR WITH LOCKING MEANS 3 Sheets-Sheet 1 March 20, 1962 c. c. DAVIS ETAL 2 PUSH-BUTTON OPERATOR WITH LOCKING MEANS Filed Oct. 23, 1959 5 Sheets-Sheet 2 March 20, 1962 c. c. DAVlS ETAL 3,026,385

PUSH-BUTTON OPERATOR WITH LOCKING MEANS Filed on. 23, 1959 s Sheets-Sheet s United States Patent 3,026,385 PUSH-BUTTON OPERATOR WITH LOCKING MEAVS Charles C. Davis and Clyde F. Robbins, Milwaukee, Wis., assignors to Cutler-Hammer, Inc, Milwaukee, Wis., a corporation of Delaware Filed Oct. 23, 1959, Ser. No. 848,244 10 Claims. (Cl. 200-44) The present invention relates to an improved pushbutton operator with locking means.

It is an object of the present invention to provide an improved push-button operator which may be key-turn locked in either extended, depressed, or both of such operating positions.

Another object is to provide an embodiment of the foregoing wherein the operator can be key-turn preset in extended position to automatically lock in depressed position following movement into the latter position.

And a further object is to provide a locking mechanism of the foregoing types which by simple changes in a few parts can be modified to provide any or all of the foregoing type of locking operations.

Other objects and advantages of the hereinafter appear.

The accompanying drawings illustrate preferred ernbodiments of the invention which will now be described, it being understood that the embodiments illustrated are susceptible of modification in respect of details without depmg from the scope of the appended claims.

a In the drawings;

FIGURE 1 is a top plan view of a push-button operator incorporating the improved locking means of this invention;

FIG. 2 is an elevation sectional view taken along the line 22 of FIG. 1 illustrating the push-button operator mounted on a panel and having an electric switch operatively associated therewith;

FIG. 3 is a transverse sectional view taken along the line 33 of FIG. 2 illustrating the working relation of certain parts of the locking mechanism in unlocked extended position of the push-button operator;

FIG. 4 is like FIG. 3 but shows the operative relation of the aforementioned parts of the locking mechanism in extended, locked position;

FIG. 5 is like FIGS. 3 and 4, but shows the operative relation of the aforementioned parts of the locking mechanism in depressed, locked position;

FIG. 6 is an exploded view in perspective of parts of the locking mechanism illustrated in FIGS. 1 to 5;

FIG. 7 is an exploded view in perspective of a modified subassembly of the locking mechanism afiording automatic locking in depressed position;

FIG. 8 is a view similar to FIG. 3 but shows the operative position of the modified form of locking mecha nism shown in FIG. 7 with the push-button operator in unlocked extended position;

FIG. 9 is like FIG. 8 but shows the aforementioned portion of the modified locking mechanism in key-turn preset position; and

FIG. 10 is like FIGS. 8 and 9 but illustrates the aforementioned portion of the modified form of locking mechanism attained following depression of the pushbutton operator.

As shown in FIGS. 1 and 2, one form of push-button operator constructed in accordance with this invention comprises a housing 10, a push-button 12, reciprocally movable within a cylindrical barrel portion 10a of a housing 10, a lock barrel 14 which is rotatable upon insertion of a key 16 into a slot in the outer end thereof, a compression spring 18 which biases push-button operator outwardly of the barrel 10a, a latch plate 20 non-rotatinvention will ice ably secured to a shaft 22, which in turn is non-rotatably secured to the end of lock barrel 14, and a push-plate 2.4 rotatably mounted on shaft 22 adjacent the lower end of the latter. Housing 10 has an integral flange portion 10b extending transversely of barrel portion 10a at one end thereof and an electric switch 26 is secured thereto by screws 28 taking into threaded openings life in the flange portion. While not limited to any particular form, the switch 26 in one preferred form is of the type disclosed in the Nolden and Robbins Patent No. 2,930,- 859, issued March 29, 1960. The push-button operator of the present invention with the electric switch 26 may be secured to a panel, such as a panel 30, by the barrel portion 10a projecting through a suitable clearance aperature 300! formed in panel 30 and a retaining nut 32. being taken down on the outer threaded portion 10d of the housing 10. As depicted, a suitable gasket washer 34 is interposed between the flange portion 10b and one side of the panel 30 and a portion of a flat name or indicia plate 36 is disposed between the undersurface of the retaining nut 32 and the outer side of the panel 30.

As best shown in FIG. 6, push-button 12 comprises an upper cylindrical portion 12a having twelve vertically extending recesses 12b formed at equally spaced rotary angles of 30 in the outer surface thereof. Six of the recesses 12b accommodate and fit about a like number of inwardly projecting, longitudinal ribs 10e formed at equally spaced rotary angles of 60 on the inner surface of the barrel portion 10a of housing 10. This interfit prevents any substantial rotary movement of the pushbutton within the barrel 10a and engagement with the upper end of a recess 12b with the upper end of a rib 10e, limits the degree of inward movement the pushbutton is permitted in the barrel 10a. In the inner bore 12c of the push-button are formed six inwardly projecting, longitudinal ribs 12d which are spaced at rotary angles of 60. When no key is inserted in the lock barrel 14, lock plungers 14b thereof are adapted to extend in the spaces between pairs of the ribs 121; and hold the lock barrel in a given rotary position in push-button 12. As will be understood, the insertion of the key 16 into key slot 14a afiords retraction of the lock plungers 14b whereupon the lock barrel may be rotated by turning of the key to a different rotary position.

Adjacent to its lower end, the push-button 12 is provided with an end portion of reduced diameter 12e which at its extreme end is provided with a saw-toothed surface 12 Lock barrel 14, at its inner end is provided with four downwardly projecting cylindrical studs which extend through a rectangular opening formed in a detent spring disk 38. Spring disk 38 is provided with transversely extending convex portion 38a which is adapted to seat on its outer surface within the trough of the saw-toothed surface 12 in the end of the portion 12e of the push-button 12. The studs 14c extend through suitable clearance openings formed in a circular plate 40 to which the shaft 22 is non-rotatably secured at one end thereof. The studs 140 are upset against the opposite surface of the plate 40 to hold lock barrel 14, plate 40, shaft 22, and spring 38 in non-rotatable assembled relation to each other. Spring disk 38, in its interfitting relation with the surface 129, affords a positive rotary feel of change and attainment of position when a key 16 is inserted in the lock barrel 14 and rotated from one operating position to another.

Compression spring 18 seats at one end against a shoulder formed at the juncture between the portion 12a and 122 of push-button 12 and at its other end seats against an annular steel washer 42 disposed about the upper surface of a flanged base portion 44a of a rubber sealing diaphragm 44 which has a conical portion 44b. The conical portion 44b has a central aperture 44c formed therein and edge portions of the diaphragm surrounding such aperture elastically fit in an annular recess 22b formed in the shaft 22. On its lower surface the flange portion 44a of diaphragm 44 seats against a radially inwardly extending shoulder formed in barrel 10a. In the assembled relation shown, diaphragm 44 seals against the entry of oil, moisture, and dirt therebelow.

As best shown in FIG. 2, shaft 22 is provided with a portion 220 which has two parallel fiat surfaces and the upper end of the cup portion 20a of latch plate 20 has an opening complementary thereto which non-rotatably accommodates the portion 220. Adjacent to its lower end, shaft 22 is upset over the lower surface of a central boss portion 24a of the push-plate 24 and a washer 46 is disposed between the upset end portion of the shaft 22 and the portion 24a. A compression spring 48 is disposed at one end about the circular boss portion 24a of push-plate 24 and at its upper end seats against a washer 50 which is disposed about shaft 22 and seats on the inner surface of the cup portion 20a of latch plate 20. Spring 48 serves to resiliently space apart the latchplate 20 and the push-plate 24 on the shaft 20. The upper surface of the portion 20a seats against a shoulder formed by the juncture ofthe aforementioned portion 220 and a cylindrical portion of greater diameter 22d. Push-plate 24 on its lower surface is provided with oppositely disposed, outwardly and upwardly extending pairs of bifurcated limbs 2412. On each side thereof, displaced at right angles to said pairs of bifurcated limbs the pushplate is provided with the wedgeshaped portions 24c which on the lower surfaces thereof are adapted to engage with switch operating members, such as the plungers 26a of electric switch 26. Each pair of bifurcated limbs 24b is disposed on opposite sides of the longitudinally extending ribs 10g formed in the lower inner surface of barrel portion 10a to non-rotatably guide push-plate 24 in barrel 10a.

Referring to FIGS. 3 to 6, it will be seen that the latch plate 20 is provided with an integral flanged portion 20b. Portion 20b is provided with radially inwardly extending notches 200 which lie diametrically opposite the central axis of plate 20. Deeper, but narrower, notches 20d which communicate with the notches 200 also are disposed diametrically opposite the central axis of plate 20. In the operating position of. the key-turn lock barrel depicted in FIGS. 1, 2 and 3, latch plate 20. (see FIG. 3) is positioned so that the notches 20d are alined to afford clearance therein for the ribs 10g. Accordingly, as push-button 12 is depressed inwardly of the barrel portion 10a, shaft 22, latch plate 20, and pushplate 24 will freely move downwardly with push-plate 24 moving switch operator 26a inwardly of the switch 26. When push-button 12 has reached the limit of its travel inwardly of barrel portion 10a, bifurcated portions 24b will move below the lower end of ribs 10g. Portions adjacent the extreme ends of portions 241) will straddle the ribs 101' which merge at their upper ends at a shoulder with the ribs 10g. Thus with the portions 24b either straddling the ribs 10 or 10g, the latter is restrained against any rotary movement. If switch operator 26a reaches its limit of travel inwardly of switch before pushbutton 12 reaches its limit of inward travel, spring 48 will compress to afford over-travel protection.

Let it be assumed that initially the lock barrel 14 is in'the position depicted in FIG. 1 and that push-button 12 is in its normal extended position depicted in FIG. 2. Now if key 16 is turned counterclockwise 60 as viewed in FIG. I, lock barrel 14, shaft 22, and consequently latch plate 20 will be rotated counterclockwise therewith. Latch plate 20 will'then rotate until the flange 20b forming one margin of the notches 20d engage the other side of the stop ribs 10h. It will then assume the position depicted in FIG. 4. It will be seen that in this position, portions of the flange 20b overlie the upper ends of the ribs 10g. If key 16 is then removed from the lock barrel 14, it will not be possible to move the push-button 12 inwardly to operate switch 26. As the lock plungers 14b will then be engaged between adjacent pairs of ribs 12d in push-button 12, latch plate 20 will be retained in that position until key 16 is again inserted and the lock barrel moved clockwise. The operating position thus attained is termed the locked-up position.

Now let it be assumed that the push-button operator is in the initial operating positions depicted in FIGS. 1 and 2 and that push-button 12 is pushed inwardly to its extreme limit, Then let it be assumed that in such extreme limit of push-button 12, key 16 is turned clockwise 60 to its extreme limit. Lock barrel 14, shaft 22, and latch plate 20 will thus be roated in a clockwise direction. Latch plate 20 in so turning in the clockwise direction will have unnotched parts of its flange 20b rotated in position under the lower edge of the ribs 10g. In such position the operator 260 will be held in its inward position in switch 26 and push-button 12 will also be held in an extreme inward position in the barrel 10a. This position is termed the locked-down position of the pushbutton operator. If key 16 is subsequently rotated counterclockwise to the position depicted in FIG. 1, latch plate 20 will assume the operating position depicted in FIG. 3

and push-button 12, under the bias of compression spring.

18, will be returned to the normal extended operating position depicted in FIG. 2.

As will be noted from the foregoing, the embodiment depicted in FIGS. 1 to 6 affords; (a) unlocked normal momentary type of operation, (b) locked in extended position afirording prevention of operation of the pushbutton inwardly, and (c) locked-down in operated position to hold a switch in a given operating condition continuously.

FIG. 7 shows a modified lock plate and shaft assem bly which affords automatic locking in the inner push button position following key-turn preset in extended position of the push-button 12. In this modified version a latch plate 60, having a cup-shaped portion 60a in which is formed a central circular opening 60b, is disposed about a shaft 61, the cylindrical portion 615. thereof rotatably penetrating the opening 6%. As will be understood, without more, latch plate 60 would be freely rotatable on shaft 61. A clutch plate 62, having-an annular portion 62a and an integral right angle lug portion 62b, is disposed about shaft 61 so that a substantially rectangular opening 620 is disposed about in non-rotatable relation, a complementally formed portion 616 011 the shaft 61. The lug 62b extends through an arcuate slot 600 formed in the end of portion 60a of latch plate 60. A torsion spring 63 is disposed about shaft 61 and one end thereof is anchored about a struck-up portion 60d in the upper surface of the cup portion 60a of latch plate 60. The opposite end of the torsion spring 63 is anchored about the upstanding lug 62b of clutch plate 62. The flange portion 60c is formed with pairs of diametrically opposed notches 60 and 60g which correspond identically with the notches 20c and 20d of latch plate 20 of the form aforedisclosed in connection with FIGS. 1 to 6. It may also be assumed, that except for the modification just described, the modified push-button operator is in other respects like that disclosed in connection with FIGS. 1 to 6. 7

Let it be assumed that the modified push-button operator is in the position depicted in FIGS. 1 and 2. Shaft 61 and plate 62 will assume the rotary position in barrel 10a depicted in FIG. 8 wherein notches 60g 'are disposed about the ribs 10g to permit free inward movement of latch plate 60, shaft 61 and push-button 12. Now let it be assumed that in such position the key 16 is rotated 60 in the clockwise direction. Lock barrel 14 and shaft 61 will thus be rotated in the clockwise direction. Due to the rotatable clearance afiorded by the opening 6% in latch plate 66 in relation to the portion 61b of shaft 61, latch plate 66 would not be directly rotated. However, as clutch plate 62 is non-rotatably mounted on shaft 61,

it is caused to rotate with it in the clockwise direction to tighten the turns of coil torsion spring 63, with the right-hand end 63a thereof being moved from the position depicted in FIG. 8 to that depicted in FIG. 9. With spring 63 coiled more tightly, it would tend to rotate latch plate 60 in the clockwise direction. However, as ends of the notches 60f engage with the ribs 10g in barrel portion 10a, latch plate 60 is prevented from any appreciable clockwise rotation.

Now let it be assumed that after key 16 has been turned to its clockwise extreme position to afford the cocking of torsion spring 63 aforedescribed, it is removed from lock barrel 14, thereby allowing plungers 14a to reengage between adjacent ribs 12d formed in the inner surface of push-button 12. With lock plungers so engaged, lock barrel 14, and consequently shaft 61 and clutch plate 62, are prevented from moving in the counterclockwise direction under the bias of the tightened torsion spring 63.

If push-button 12 is moved inwardly to its extreme limit wherein the upper surface of the flange portion 60c is moved below the lower end of the ribs 10g, latch plate 60 will be rotated in the clockwise direction from the position depicted in FIG. 9, to the position depicted in FIG. 10, under the bias of torsion spring 63. In the position depicted in FIG. 10, parts of the flange 60e underlie the lower ends of the ribs 10g and thus latch plate 60, shaft 61, lock barrel 14, and push-button 12 will be restrained from movement outwardly relative to lock barrel portion 10a. Consequently push-plate 24 will be held in the inward position to hold switch operator 26a in its inward position in switch 26.

With latch plate 60 in the position depicted in FIG. 10, let it be assumed that key 16 is again inserted in lock barrel 14 and the latter is rotated 60 in the counterclockwise position to that position depicted in FIG. 1. As the lug 62b will be engaged in the right-hand end of the arcuate slot 60c of latch plate 60, the turning of the lock barrel 14 in the counterclockwise direction will eifect rotation of shaft 61, clutch plate 62 and latch plate 60 in the counterclockwise direction to the position depicted in FIG. 8 wherein push-button 12, lock barrel 14, shaft 61, latch plate 60 and push-plate 24 can return to extended unlocked position under the bias of compression spring 18.

Assuming that latch plate 60 is in the rotary position depicted in FIG. 8 and key 16 is turned counterclockwise, it will be seen that as lug 62b engages the upper end of slot 620, latch plate 61"; will be rotated in unison with lock barrel 14, shaft 22, and clutch plate 62 to afford a locked-up position of push-button 12 similar to that afforded by the embodiment illustrated in FIGS. 1 through 6.

If desired, one or the other of the locked-up or locked-down operating positions can be omitted. By extending the ribs 10g upward to meet the shoulder 10f in barrel portion 10a, the notches 10j will be eliminated, thereby preventing any rotary movement of latch plates 20 or 60 in the outer extended position of push-button 12. In the embodiment of FIGS. 1 to 6, by extending ribs 10g to the lower end of barrel portion 10a, rotation of latch plate 20 in the inner extreme position of pushbutton 12 will be prevented.

Where a plurality of push-button operators are mounted on a panel, a particular alinement of the switches secured to the operator housings 10 on the rear side of the panel may be desired. Normally the desired alinement of the switches would be either horizontal, parallel with the top and bottom edges of the panel, or vertical, parallel with the side edges of the panel. Depending upon the desired alinement and whether the switches run in one direction or 180 reversed to such direction in the desired alinement, the housing 10 of a given pushbutton operator could have four different 90 rotary spaced mounted positions on the panel. For the assemled relation of the operation depicted in FIGS. 1 to 6, this would mean that the key slot 14a in look barrel in normal unlocked position could be, as shown in FIG. 1, inverted 180 or run horizontally either right or left. Normally it is desirable to have the center position of the key slot run vertically or parallel with the side edges of the panel and so the notched edge of the key when inserted is lowermost. The construction of the present push-button operator permits this to be readily provided in assembly of the operators as will now be described.

Assume that for a desired alinement of switches on the rear of the panel, that housing 10 would have to be rotated counterclockwise from that depicted in FIG. 1. To provide for vertical alinement of key slot 14a in center position, lock barrel 14 would have to be rotated 90 clockwise in push-button 12. Howevenif lock barrel 14 is so rotated the tumblers would aline with one of the ribs 12:1 in push-button 12 as the spaces between the ribs are 60 apart and could not be locked so that the key slot 14a would be in the desired vertical relation; it would be at an angle of 30 to the vertical. Now assuming that the foregoing rotations have been made, if pushbutton 12 is rotated 30 one way or the other in barrel portion 10a, the lock plungers 14b will then fall in a space between adjacent ribs 12d in push-button 12 to provide the desired vertical alinement of key slot 14a in center position of the lock barrel. It will also be apparent that if housing 10a is rotated 90 counterclockwise, and lock barrel 14 is rotated 90 clockwise, as aforedescribed, that the assembly comprising latch plate 20, shaft 22 and plate 40, will have to be rotated 90 counterclockwise before being secured to lock barrel 14 to insure the proper relationship of latch plate 20 to the ribs 10g and 101' of the barrel portion 10a. It will be apparent that the same considerations will hold when housing 10 is rotated in the opposite direction, or instead of 90, and that the reverse rotation of lock barrel 14 and corresponding rotation of latch plate 20, shaft 22 and plate 40 wil be commensurate therewith while the correcting rotation of push-button 12 will only have to be 30 in either direction to desired normal vertical relation of the key slot 14a.

We claim:

1. A lockable push-button operating mechanism comprising, in combination, a tubular casing, a push-button mounted in said casing for reciprocal movement therewithin, a lock barrel mounted in the outer end of said push-button and rotatable within the latter upon insertion of key from a given position to at least one other position rotarily spaced therefrom and vice versa, a shaft disposed within said casing and secured to said lock barrel for rotation by the latter, an operating member mounted on said shaft and movable axially in said casing by corresponding movement of said push-button, and a latch member disposed in said casing and mounted on said shaft for rotary movement corresponding to that of said lock barrel, said latch member and the interior of said casing being formed so that in said given position of said lock barrel said latch, said operating member and said shaft are free to be reciprocably moved in said casing by corresponding movement of said push-button, while in said one other position of said lock barrel a portion of said latch plate when said push-button is in a given extreme position axially of said casing engages with a portion formed on the interior of said casing to prevent axial movement of said latch, said shaft, said operating member, and said push-button in one direction.

2. The combination according to claim 1, wherein said lock barrel is rotatable to said other position when said push-button is in its outwardly extended position in said casing and is also rotatable to a third rotary spaced position from said given position when said push-button is depressed inwardly a predetermined amount to rotate said latch member to a corresponding position wherein 5 a certain other portion thereof engages with said portion formed on the interior of said casing to hold said pushbutton, said shaft and said operating member in an in ward operating position in said casing.

3. The combination according to claim 1, wherein said portion formed on the interior of said casing comprises at least one inwardly projecting rib and said portion of said latch member comprises a circular disc having at least one radial notch for clearance alinement with said rib in said given rotary position of said lock barrel and wherein a portion of the disc web engages with one end of said rib in said one other position of said lock barrel.

4. The combination according to claim 2, wherein said latch member has a torsion spring, lost motion driving connection with said shaft whereby said lock barrel may be rotated upon insertion of said key in extended position of said push-button to said third position to stress torsion spring to afford automatic rotation of said latch plate to said corresponding position following depression of said push-button inwardly said predetermined amount.

5. A lockable push-button operating mechanism comprising,'in combination, a cylindrical casing, a cylindrical push-button mounted for reciprocal, non-rotatable movement in the bore of said casing, a lock barrel mounted in the bore of said push-button and which upon insertion of a key is rotatable from a first to a second and third rotary spaced positions and vice versa for locking in any of such positions by removal of the key, a spring disposed in said casing and'biasing said push-button to an outwardly extended position in said casing, a shaft axially disposed in said casing and non-rotatably secured to said lock barrel, an operating member rotatably mounted on said shaft and non-rotatably guided in said casing for reciprocal movement by corresponding movement of said push-button, and a latch member mounted on said shaft for rotation thereby inresponse to the aforementioned rotation of said lock barrel, said latch member and the interior of said casing being so formed that in said first position of said lock barrel said push 'button is freely reciprocably movable in said casing to aiford corresponding movement of said operating member, that in said second position of said lock barrel a portion of said latch member engages with a portion onrthe interior of said casing to prevent movement of saidpush-button inwardly of said casing, and that in said third position of said lock barrel attained following movement of said push-button inwardly of said casing another portion of said latch member engages with said portion of the inten'or of said casing to prevent outward movement of said push-button under the bias of said spring.

6. The combination according to claim 5, wherein said push-button is saw-toothed at the inner end thereof and a detent spring is non-rotatably mounted with said shaft and said lock barrel is adapted to yield as it rides over the saw teeth and snap into place in the intermediate notches between saw teeth when said lock barrel reaches one of said first second or third rotary positions to provide positioning and attaining feel.

7. The combination according to claim 6, together with an elastic diaphragm having a central aperture through which said shaft extends in elastic sealed engagement and a peripheral flange held in sealing engagement with an annular shoulder formed in the interior of said casing by the inner end of said compression spring bearing thereagainst.

8. The combination according to claim 7, together with a second coiled compression spring disposed about said shaft and bearing at its opposite ends against said latch member and said operating member to aiford yielding axial movement of the latter on'said shaft when'the opposing force on said operating member exceeds that of the last mentioned spring.

9. The combination according to claim 8, wherein said operating member is non-rotatably guided in said casing by oppositely disposed bifurcated arms straddling said inward extending ribs.

10. A lockable push-button switch comprising, in combination, a casing having a cylindrical barrel and an integral laterally extending flange at one end of said barrel for abutting on the inside of an apertured panel, a retaining nut taking down on an outer threaded portion of said barrel to secure said casing to the panel, an electric switch mounted on said flange and having an external operator extending-into said barrel, a push-button mounted for axial movement in said barrel, a lock barrel mounted in said push-button wherein it is rotatable upon insertion of a key between first and second spaced rotary positions wherein it may be locked upon removal of the key, a shaft non-rotatably secured to said 'lock barrel, a latch plate mounted on said shaft for rotary movement corresponding to that of said lock barrel, said latch plate and the interior of said barrel being formed so that in the first position of said lock barrel said push-button, said shaft and said latch plate' are freely movable axially in said barrel in reverse directions and so that in said second position of said lock barrel attained following movement of said push-button to one axial extreme position said portion of said latch plate engages with a portion on the interior of said barrel to prevent movement oftsaid push-button, said shaft and said latch plate in one axial direction, an operating member engaging with the switch operator and rotatably mounted on said shaft and non-rotatably guided in the interior of said barrel, and a compression spring disposed about said shaft between said latch plate and said operating member to hold the same in a spaced relation and afford relative axial movement between said shaft and said operating member.

References Cited in the file of this patent UNITED STATES PATENTS 2,060,951 Rae et al. Nov. 17, 1936 2,605,630 Keeler Aug. 5, 1952 2,724,958 Psik Nov. 29, 1955 2,778,891 Jacobi Jan. 22, 1957 2,803,716 Nolden et a1. Aug. 20, 1957 2,930,859 Nolden et a1. Mar. 29, 1960 FOREIGN PATENTS 463,968 Great Britain Apr. 8, 1937 

